Magnetic recording member with binder therefor

ABSTRACT

A MAGNETIC RECORDING MEMBER SUCH AS TAPE OR STRIPED MOTION PICTURE FILM WHEREIN A LAYER OF FERROMAGNETIC PARTICLES IS BOUND ON A SYNTHETIC RESIN WEB BY A BINDER CONSISTING ESSENTIALLY OF CELLULOSE NITRATE IN INTIMATE MIXTURE WITH A POLYMERIC COMPOSITION CONSISTING ESSENTIALLY OF, BY WEIGHT, 50-80% VINYLIDENE CHLORIDE, 2-30% ACRYLONITRILE, AND 0-60% OF METHYL METHACRYLATE OR ACRYLATE OR HYDROXY PROPYL METHACRYLATE. THIS BINDER IS ESPECIALLY GOOD FOR POLY(ETHYLENE TEREPHTHALATE) WEBS. BEST ADHERENCE TO A WEB IS SECURED WHEN THE FERROMAGNETIC PARTICLES AND THE ABOVE BINDER ARE DEPOSITED FROM AN ORGANIC SOLVENT WHEREIN AT LEAST 8% OF THE SOLVENT IS N,N-DIMETHYL FORMAMIDE OR ACETAMIDE.

United States Patent Ofiice 3,713,87 Patented Jan, 30, 1%?3 3,713,887 MAGNETIC RECORDING MEMBER WITH BINDER THEREFOR Ronald M. Stimson, Rochester, N .Y., assignor to Eastman Kodak Company, Rochester, N.Y. No Drawing. Filed May 1, 1970, Ser. No. 33,969 Int. Cl. G03c 1/80, J/84;G11b 5/62 US. Cl. 117-235 3 Claims ABSTRACT OF THE DISCLOSURE A magnetic recording member such as tape or striped motion picture film wherein a layer of ferromagnetic particles is bound on a synthetic resin web by a binder consisting essentially of cellulose nitrate in intimate mixture with a polymeric composition consisting essentially of, by weight, 50-80% vinylidene chloride, 2-30% acrylonitrile, and 060% of methyl methacrylate or acrylate or hydroxy propyl methacrylate. This binder is especially good for poly(ethylene terephthalate) webs. Best adherence to a web is secured when the ferromagnetic par ticles and the above binder are deposited from an organic solvent wherein at least 8% of the solvent is N,N-dimethyl formamide or acetamide.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to applying a tightly adherent coating to a Web of synthetic resin, particularly to a polymeric linear terephthalate ester film such as poly- (ethylene terephthalate). More particularly, the invention is concerned with applying a tightly adherent coating of a magnetic recording composition to such a web in the form of photographic motion picture film or magnetic recording tape, and with the resulting product. Additionally, the invention relates to novel compositions that can be used for binding a magnetic material to such a web; and to a novel composition that can be used successfully for binding a magnetic material to both poly(ethylene terephthalate) webs and to cellulose ester webs.

Prior art Magnetic stripes have been successfully applied to photographic film having a cellulose ester base by employing the compositions described in US. Pat. 3,220,- 843. These compositions are particularly advantageous because they will strike through the antihalation layer normally present on photographic film and will adhere directly to the cellulose ester web rather than to the antihalation layer itself. This is essential because the antihalation layer is normally dissolved off the web during the developing of the photographic film in alkaline solutions.

When the web is poly(ethylene terephthalate), with or without an antihalation layer or an antistatic layer on the back of the film, I have found that the compositions of Pat. 3,220,843 do not adhere tightly, apparently because poly(ethylene terephthalate) is much more inert than cellulose esters.

The removable antihalation and antistatic layer to which the magnetic striping is applied are those customarily used on polyester photographic films, which are removed from the film during processing in alkaline solutions. Such layers are disclosed in US. 2,976,168. Some polyester films carry a non-removable antistatic layer such as that disclosed in U.S. 3,437,484. The magnetic stripping composition must strike through either of these layers to the base to obtain good adhesion. Sometimes the magnetic stripes are applied to the emulsion side of the film.

SUMMARY OF THE INVENTION In accordance with the present invention the tight adherence of a magnetic recording composition to a poly- (ethylene terephthalate) base, such as photographic film or a magnetic tape, is accomplished by applying the magnetic composition as a dispersion of ferromagnetic particles in a solvent-binder composition comprising in percents by weight:

(A) A resinous binder phase which consists essentially of 20 to 80% of low or high viscosity cellulose nitrate, in intimate mixture with 80 to 20% of a polymeric composition consisting essentially of 50 to 80% of vinylidene chloride, 2 to 30% of acrylonitrile, and 0 to 60% of a lower alkyl unsubstituted or hydroxy substituted acrylic or methacrylic ester, and

(B) A solvent phase comprising one or more vaporizable organic solvents, at least 8% of which is a lower N,Ndialkylamide of a lower aliphatic acid such as N,N- dimethyl formamide or N,N-dimethyl acetamide.

When none of the acrylic or methacrylic ester is used, the polymeric composition is known as a copolymer; and when acrylic or methacrylic ester is used the polymeric composition is known as a terpolymer.

Advantageously, the resinous binder phase (A) constitutes 5 to 40%; and the solvent phase (B) constitutes 60 to 95% of the solvent-binder composition.

Preferred ranges within the broad operable ranges set forth above for the resinous binder phase are 50 to of cellulose nitrate and 50 to 30% of the polymeric composition. In general the best results are secured when using a 1:1 ratio of cellulose nitrate to the polymeric composition in the resin phase; and when using at least about 30% of N,N-dimethyl formarnide in the solvent phase.

I have found that magnetic stripes or layers adhere with remarkable strength to a poly( ethylene terephthalate) web when my novel binder compositions are employed. I have found it particularly advantageous, when depositing one or more magnetic stripes on a poly(ethylene terephthalate) film base having an antihalation layer, for the binder materials and ferromagnetic particles to be dispersed in an easily vaporizable organic solvent or mixture of solvents which cause the composition to strike through the antihalation layer and adhere tightly to the poly(ethylene terephthalate) base material. Suitable essential organic solvents are a lower N,N-dialkyl amide of a lower aliphatic acid, for example, N,N-dimethyl formamide with or without N,N-dimethyl acetamide, which can be combined with other solvents such as 2- ethoxy ethanol, Z-butoxyethanol, methyl ethyl ketone, n-butanol or amyl acetate. The small quantities of nbutanol in the examples accompany the cellulose nitrate as purchased, but this solvent is not essential to operability.

Other materials can be used in the compositions to provide some desirable effects, without modifying the essential activity of the principal ingredients. For example, surfactants and plasticizers can be included without materially affecting adherence of the stripes.

After deposition of the magnetic compositions described above, the web of poly(ethylene terephthalate) is passed through a drying zone wherein the solvents evaporate, leaving on the web a layer of ferromagnetic particles embedded in a resinous binder mixture consisting essentially of cellulose nitrate (advantageously 20 to and the polymeric composition (advantageously 80 to 20%) consisting essentially of 50 to 80% of vinylidene chloride, 2 to 30% of acrylonitrile, and 0 to 60% of lower alkyl unsubstituted or hydroxy substituted acrylic or methacrylic ester, all percents being by weight.

On striped motion picture film the finished stripes generally are about 0.4 mil thick and may be 12, 30, or 100 mils wide, whereas the film is much wider, e.g. 8 or 16 mm.

The aforementioned acrylic ester-containing terpolymers may be prepared by known methods such as emulsion polymerization or the like. Especially useful terpolymers are those comprising vinylidene chloride, acrylonitrile, and unsubstituted or hydroxy substituted lower alkyl acrylic esters. Particularly useful terpolymers have from about 50-80% vinylidene chloride, about 230% acrylonitrile and about 1-60% unsubstituted lower alkyl acrylic ester, especially wherein the lower alkyl acrylic ester may be a lower alkyl acrylate residue wherein the lower alkyl has 1-4 carbon atoms, e.g. methyl acrylate, ethyl acrylate, etc. or a lower alkyl alkacrylate, wherein the lower alkyl has 1-4 carbon atoms, and where the alk-prefix in alkacrylate represents an alkyl group of 1-4 carbon atoms, e.-g. methyl methacrylate, ethyl methacrylate, butyl methacrylate.

Other especially useful terpolymers are those containing an hydroxy substituted lower alkyl acrylic ester. Examples of these hydroxy substituted lower alkyl acrylic esters are hydroxypropyl acrylate and hydroxypropyl methacrylate. A particularly useful range is from about 50-80% vinylidene chloride, about 230% acrylonitrile and about 1-60% hydroxy substituted lower alkyl acrylic ester.

With respect to the above-described substituted and unsubstituted acrylic ester-containing terpolymers it will be appreciated that other ratios of the monomeric substituents may be used providing the products are sufficiently soluble in the solvent stage. The molecular weight of the resulting polymer may also be varied, but an especially useful molecular weight range is characterized by an inherent viscosity of from about 0.10 to 0.65, particularly from about 0.15 to 0.25 deciliter/ gram in N,N-dimethyl formamide.

When using a copolymer instead of the terpolymer, the same technique is followed but the acrylic ester is omitted.

The magnetic materials of the striping composition can vary in magnetic properties, such as permeability and coercivity. Ferromagnetic materials of well known types such as acicular magnetic iron oxide (gamma ferric oxide) can be used. Desirable properties can be obtained by varying the ingredients of magnetic compositions. Thus magnetizable alloys are useful, for instance, alloys with iron or copper, aluminum, nickel, cobalt, and carbon, one component thereof being non-magnetic in most cases. The magnetic materials may be prepared as finely divided particles by various methods including the thermal decomposition of the corresponding metal car'bonyls. Iron prepared from iron carbonyl may be employed, but iron alloys prepared from mixtures of metal carbonyls may also be used as, for example, iron alloys with nickel, cobalt, chromium, tungsten, or molybdenunnThe methods of U8. Pat. No. 2,694,656 may, for example, be used for preparing suitable ferromagnetic materials. The IRN magnetic iron oxides manufactured by the C. K. Williams Co., 640 N. St., Easton, Pennsylvania, are very useful, e.g. MO-4030 magnetic iron oxide or MO-203S magnetic iron oxide having higher coercivity.

The proportions of binder to magnetic oxide or its equivalent in the final dried coating may vary from about 1:1 to 1:5 by weight.

THE PREFERRED EMBODIMENTS The following examples illustrate the principles of the invention in greater detail. In all of the examples the dispersions are ball-milled for 6 or 7 days or until the particle size of the magnetic iron oxide (7 ferric oxide in every example) is judged to be satisfactory. The dispersions are then coated on the antihalation coating of poly (ethylene terephthalate) motion picture film to form a narrow stripe adjacent to each edge of the film, the so]- vents are allowed to evaporate, and the adhesion of the stripes is tested by (a) dry stripping wherein a sticky tape such as Scotch brand tape of the 3M Company is applied to the stripe and then pulled off; and (b) a caustic dip adhesion test wherein sample lengths of striped film are placed in aqueous NaOH solutions (.1 N and 2.5 N) and subjected to 1 minute of ultrasonic vibration. The samples are then washed and dried, and then subjected to the dry stripping test described in (a) above.

EXAMPLE 1 Dispersion: Percent Gamma ferric oxide 31.5 Terpolymer (IV=.20, .54 and .68) 6.7

sec. SS cellulose nitrate (30% Wet with alcohol) 6.7 Z-ethoxyethanol 21.0 N,N-dimethylformamide 34.1

*Methyl methacrylate 20%, vinylidene chloride 60%, acrylonitrile 20%.

Percent Binder of Final coating finalcoating Terpolymer 16. 6 59 Cellulose nitrate 10. 9 41 Gamma ferric oxide 73. 5

Good adherence to poly(ethylene terephthalate) web having a resin base antihalation layer.

Good adherence to poly(ethylene terephthalate) web having a resin base antihalation layer.

EXAMPLE 3 Dispersion: Percent Gamma ferric oxide 31.0 Terpolymer* (IV=.20) 9.9

sec. SS cellulose nitrate (30% wet with alcohol) 4.8 2-ethoxyethanol 20.6 N,N-dimethylformamide 33.7

*Same as Example 1.

Percent Binder of Final coating final coating Cellulose nitrate- 7. 7 25 Terpolymer. 22. 3 Gamma ferric oxi 70. 0

Good adherence to poly(ethylene terephthalate) web having a resin base antihalation layer.

Good adherence to unsubbed p ly( y e p thalate) web.

Good adherence to poly(ethylene terephthalate) web having resin base antihalation layer.

EXAMPLE Dispersion: Percent Gamma ferric oxide 30.5 Terpolymer* 6.5

sec. SS cellulose nitrat (30% wet with alcohol) 9.3 Methyl ethyl ketone 8.9 Z-ethoxyethanol 15.4 N,N-dimethylformamide 29.4

*30% methyl acrylate, 66.5% vinylidene chloride, 3.5% acrylonitrile.

Percent Binder of Final coating final coating Cellulose nitrate r 15. 0 50 Terpolymer. 15. 0 50 Gamma ferric oxide 70.0

Good adherence to poly(ethylene terephthalate) web having resin base antihalation layer, to unsubbed poly (ethylene terephthalate) web.

EXAMPLE 6 Dispersion: Percent Gamma ferric oxide 30.5 Copolymer* 6.5 A see. SS cellulose nitrate (30% Wet with alcohol) 9.3 2-ethoxyethanol 20.4 N,N-dimethylformamide 33.3 *75% vinylidene chloride, 25% acrylonltrile.

Percent Binder of Final coating final coating Cellulose nitrate 15.0 50 15.0 50 Gamma ferric oxide 70. 0

Adherence same as in Example 5.

EXAMPLE 7 Dispersion: Percent Gamma ferric oxide 26.1 Terpolymer* (IV=.20) 5.7 40-60 sec. SS cellulose nitrate 5.7 2-ethoxyethanol 20.0 N,N-dimethylformamide 33.9 N,N-dimethylacetamide 6.9 n-Butyl alcohol 1.7 *Same as Example 1.

Percent Binder of Final coating final coating Cellulose nitrate 1..-... 15. 2 50 Terpolymer l5. 2 50 Gamma ferric oxide 69. 6

Adherence same as in Example 5.

6 EXAMPLE 8 Dispersion: Percent Gamma ferric oxide 24.0 Terpolymer* (IV=.68) 6.0 40-60 sec. SS cellulose nitrate 6.0 2-ethoxyethanol 12.0 Methyl ethyl ketone 12.0 N,N-dimethylformamide 30.8 NN-dimethylacetamide 7.3 n-Butyl alcohol 1.9

*Same as Example 1.

Percent Binder of Final coating final coating Cellulose nitrate 16.7 50 Terpolyrner 16. 7 50 Gamma ferric oxide 66. 6

Good adherence to poly(ethylene terephthalate) web having resin base antihalation layer or an antistatic layer.

EXAMPLE 9 Dispersion: Percent Gamma ferric oxide 26.5 Terpolymer* 5.8 40-60 sec. SS cellulose nitrate 5.8 Amyl acetate 19.9 2-butoxyethanol 27.8 N,N-dimethylformamide 12.0 n-Butyl alcohol 2.2

*Same as Example 1.

Percent Binder of Final coating final coating Cellulose nitrate l6. 5 50 Terpolymer l5. 5 50 Gamma ferric oxide 69. 0

Good adherence to poly(ethylene terephthalate) web having a resin base antihalation layer.

Good adherence to emulsion side of poly(ethylene terephthalate) web.

Good adherence also would be expected on cellulose triacetate film without excessive curl occurring, whereas more than 14% of N,N-dimethylformamide causes too much curl.

This dispersion would be useful for striping motion picture film subsequent to development; and would provide exceptional operating flexibility because it can be applied to both acetate and polyester films without requiring that the film types be sequestered before striping.

EXAMPLE l0 Dispersion: Percent Gamma ferric oxide 23.6 Terpolymer* 5.2 40-60 sec. SS cellulose nitrate 2.6 300-500 sec. SS cellulose nitrate 2.6 Sorbitan tristerate 2.4 2-butoxyethanol 12.8 Methyl ethyl ketone 12.8 N,N-dimethylformamide 27.0 N,N-dimethylacetamide 9.0 n-Butyl alcohol 2.0

*Same as Example 1.

Percent Binder of Final coating final coating 40-60 sec. SS cellulose nitrate 7. 6 25 300-500 sec. SS cellulose nitrate 7. 6 25 Terpolymer 15. 3 50 Gamma ferric oxide 69. 5

7 Good adherence to unsubbed, resin jet backed, and antistatic backed poly(ethylene terephthalate).

Good adherence to emulsion side of poly(ethylene terephthalate) web.

EXAMPLE 11 Good adherence to unsubbed, resin jet, and antistatic backed poly(ethylene terephthalate) web.

Good adherence to emulsion side of poly(ethylene terephthalate) web.

EXAMPLE 12 Dispersion: Percent Gamma ferric oxide 25.1 Terpolymer" 5.4 40-60 sec. cellulose nitrate 5.4 Sorbitan tristearate 2.5 Methyl ethyl ketone 11.9 2-butoxyethanol 11.9 N,N-dimethylformamide 29.4 N,N-dimethy1acetamide 6.6 n-Butyl alcohol 1.8

*Hydroxy propyl methacrylate vinylidene chloride 67.5%, lacrylom'trile 22.5%.

P ercent B ind or of Final coating final coating Terpolymer 15 5O Cellulose nitrate 15 50 Gamma ferric oxide 70 Good adherence to unsubbed, resin jet backed, and antistatic backed poly(ethylene terephthalate). Good adherence to emulsion side of poly(ethylene terephthalate) web.

To summarize, the adherence of the magnetic stripes to poly(ethylene terephthalate) motion picture film having a synthetic resin based antihalation layer is good in every instance.

In addition, the magnetic stripes applied to unsubbed poly(ethylene terephthalate) motion picture film are judged to have good adherence in the case of Examples 3, 5, 6, 7, 10, 11 and 12, but the test was not run on unsubbed film base for the other examples.

Adherence is also good on poly (ethylene terephthalate) film base having an antistatic layer with the compositions of Examples 5, 6, 7, 8, l0, l1 and 12. Adherence is fair with the compositions of Examples 1, 2 and 4; and was not tested for Examples 3 and 9.

In contrast, when using similar copolymer and terpolymer compositions without cellulose nitrate, adherence to polyester film is not satisfactory.

On the other hand, dispersions wherein 40-60 second SS cellulose nitrate alone is the binder do not adhere to unsubbed polyester, or polyester having antihalation or antistatic coatings; and A second SS cellulose nitrate alone provides poor adherence to unsubbed polyester, and polyester having an antistatic coating.

Thus, it is evident that the compositions of the present invention are the only ones which provide good adherence to all three types of polyester webs so that one dispersion formulation suflices for striping all of the commonly produced types of polyester motion picture films.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A magnetic recording member comprising:

a web of poly(ethylene terephthalate) synthetic resin,

and

a layer of ferromagnetic particles in a binder adhering to a surface of said web, said layer being in the form of a thin stripe adjacent an edge of said web, said stripe being much narrower than said web,

said binder consisting essentially of 20 to 80% of cellulose nitrate in intimate mixture with 80 to 20% of a polymeric composition consisting essentially of 50 to 80% of vinylidene chloride, 2 to 30% of acrylonitrile, and 1 to of a lower alkyl unsubstituted or hydroxy substituted acrylic or methacrylic ester, all percentages being by weight.

2. A magnetic recording member in accordance with claim 1 wherein said binder consists essentially of 50 to of cellulose nitrate and 50 to 30% of said polymeric composition.

3. A magnetic recording member in accordance with claim 2 wherein said polymeric composition consists essentially of about 60 to 67.5% of such vinylidene chloride, about 3.5 to 22.5% of such acrylonitrile, and about 10 to 30% of such acrylic or methacrylic ester.

References Cited UNITED STATES PATENTS 3,554,794 1/1971 Geisler et al 117-235 3,547,693 12/1970 Huguenard 117-235 3,220,843 11/ 1965 Lovick et a1. 96-84 3,470,021 9/1969 Hendricx et al. 117-235 FOREIGN PATENTS 1,049,628 11/1966 Great Britain 117-235 RONALD H. SMITH, Primary Examiner US. Cl. X.R.

96-84 R, 87 R; 117-1388 F, 161 C; 252-6254 

